The present invention relates to a surface inspection method and apparatus for detecting inspection objects (such as foreign matter and scratches) on the surface of a wafer and other inspected objects.
In the conventional surface inspection apparatus, foreign matter and scratches on the surface of an inspected object are measured by placing a luminous flux incident in the form of high incidence or low incidence. However, with the trend of higher sensitivity of the surface inspection apparatus and fineness of steps, in a bare wafer (Bare-Si), a portion where a sensitivity range of detection of foreign matter and a sensitivity range of detection of scratches are superposed is smaller, which poses a problem.
Therefore, in the high sensitivity detection for placing a luminous flux in low incidence, the surface information of an inspected object is conversely less to sometimes result in a phenomenon that scratches are not detected.
On the other hand, in the detection with sensitivity sensitive to the surface information, the scratches can be detected, but the detection sensitivity of foreign matter is deteriorated.
With the trend of higher sensitivity of the surface inspection apparatus and fineness of steps, particularly in a bare wafer, there has been desired that detection of scratches as the surface information and detection of smaller foreign matter on the surface of an inspected object can be carried out simultaneously.
In the conventional surface inspection apparatus, it has been impossible to detect foreign matter with high sensitivity, and detect scratches as the surface information with high sensitivity to separate and measure both the foreign matter and scratches with high accuracy.
An object of the present invention is to enable separation and detection of both foreign matter and scratches.
The present invention provides a surface inspection apparatus and method for detecting inspection objects (such as foreign matter and scratches) on the surface of a wafer and other inspected objects.
According to one mode of the present invention, there comprises a light source section for emitting a first luminous flux and a second luminous flux; a first irradiation optical system in which the first luminous flux is irradiated on the surface of an inspected object at a first irradiation angle; a second irradiation optical system in which the second luminous flux is irradiated on the surface of an inspected object at a second irradiation angle different from the first irradiation angle; a displacement section for relatively displacing an inspected object and an irradiation luminous flux of the irradiation optical system; a light receiving optical system for receiving scattered light of the first luminous flux irradiated by the first irradiation optical system and produced from an inspection object on the surface of an inspected object and scattered light of the second luminous flux irradiated by the second irradiation optical system and produced from an inspection object on the surface of an inspected object; a first light receiving section for converting scattered light of the first luminous flux received by the light receiving optical system into a first light receiving signal; a second light receiving section for converting scattered light of the second luminous flux received by the light receiving optical system into a second light receiving signal; a inspection object distribution data forming section for forming inspection object distribution data on the basis of the first light receiving signal and the second light receiving signal; and a scratch processing section for scratch-processing the inspection object distribution data.
Preferably, a first characteristic of the first luminous flux emitted by the light source section, and a second characteristic of the second luminous flux emitted by the light source section are a wavelength of luminous flux or a polarized light component. The first irradiation angle of the first irradiation optical system is set to be smaller than the second irradiation angle of the second irradiation optical system.
Preferably, the scratch processing section processes false scratches or genuine scratches of the inspection object in the inspection object distribution data as fictitious scratches to scratch-process the inspection object distribution data to form scratch distribution data. The scratch processing section removes data of the inspection object processed as the false scratches from that of the inspection object obtained from the first light receiving signal or the second light receiving signal to thereby form foreign matter distribution data.